DOI: 10.1002/cvde.200506442 Full Paper Fabrication of Carbon Nanotube Field Emitters Using a Dip-Coating Method** By Young Il Song, Gil Yong Kim, Ha Kyu Choi, Hee Jin Jeong, Ki Kang Kim, Cheol-Min Yang, Seong Chu Lim, Kay Hyeok An, Kyung Taek Jung, and Young Hee Lee* A simple and robust dip-coating method for fabricating carbon nanotube (CNT) field emitters has been proposed. The thin multiwalled (tMW)CNTs synthesized by CVD were dispersed in various solutions such as N,N-dimethylformamide (DMF), isopropyl alcohol (IPA), N-methyl-2-pyrrolidinone (NMP), and dichloroethane (DCE). The weak adhesion between CNTs and substrate, a serious drawback of the dip-coating approach, was resolved by anchoring CNTs to the substrate via the melt- ing of an indium layer. We found that the uniformity and density of the CNTs could be optimized by controlling the degree of dispersion of CNTs in solvents. The field-emission characteristics are also discussed. Keywords: Carbon nanotubes, Dip-coating, Field emission, Field emitters 1. Introduction CNTs are attractive materials for field emitters due to their high mechanical strength and chemical stability, high electrical and thermal conductivities, and large aspect ratio with naturally formed small diameters. [1] The advent of CNTs allowed tremendous progress to be made in the fabrication of cold cathode arrays using refractory metals. The cold cathode was fabricated by evaporating refractory metals onto microhole arrays. [2] CNTs that are naturally formed with small diameters (a few tens of nanometers) can be easily fabricated using simple methods such as screen printing, in situ direct growth using CVD, self-as- sembly, and electrophoresis. [3–6] Dip-coating has several advantages over the existing methods in fabricating cold cathode field emitters. No addi- tives, such as a binder or fritz, are necessary in dip-coating, and this method can be scalable to large sizes. However, so as to obtain uniform film and hence uniformity in field- emission pattern, well-dispersed CNTs are required prior to the dip-coating in order to prevent them from being ag- gregated. Moreover, one serious drawback has been the poor adhesion between CNTs and substrate. In this report, we introduce an intermediate indium metal layer to strongly anchor CNTs to the substrate. We also improve the degree of dispersion by choosing a new type of CNTs, thin multiwalled (tMW)CNTs, and, at the same time, by optimizing the dispersion conditions by using methods such as sonication and centrifugation in various solvents. We also prove that the uniformity and density of tMWCNTs can be controlled by the number of times they are dipped. 2. Results and Discussion We synthesized tMWCNTs using catalytic (C)CVD with a FeMoMgO catalyst. The number of tube walls were 2 ∼ 6 with corresponding diameters of 3 ∼ 6 nm. Nanotube lengths were typically of the order of one micrometer. [7] They were rather straight, like MWCNTs, with a large di- ameter, and the bundle size was at most a few tens of nano- meters, much smaller than that of single-walled (SW)CNTs, which is advantageous for dispersion. The tMWCNTs re- vealed an intermediate structural characteristic between SWCNTs and typical MWCNTs, with diameters of a few tens of nanometers. The tMWCNTs are known to show better field-emission characteristics than SWCNTs and MWCNTs. Previous studies [8,9] of tMWCNTs showed a high field-enhancement factor, like SWCNTs, with the long-term emission stability comparable to MWCNTs. This indicates that tMWCNTs are as sharp as SWCNTs and as strong as MWCNTs. Therefore, we chose tMWCNTs to prepare a CNT field emitter and fabricated the tMWCNT thin film using the dip-coating process then investigated its field-emission properties. Chem. Vap. Deposition 2006, 12, 375–379 © 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 375 – [*] Prof. Y. H. Lee, Y. I. Song,G. Y. Kim, H. K. Choi, H. J. Jeong, K. K. Kim, Dr. C.-M. Yang, Dr. S. C. Lim, Dr. K. H. An Department of Physics and Center for Nanotubes and Nanostructured Composites, Sungkyunkwan University, Suwon 440-746 (Korea) E-mail: leeyoung@skku.ac.kr Dr. K. T. Jung Samsung Corning Co., LTD 472 Sin-dong, Paldal-gu, Suwon 442-732 (Korea). [**] This work was financially supported by MOE, MOCIE, and MOLAB through the foresting project of laboratory of excellence and in part by the MOST through the CNNC and by the SAINT at SKKU. We also thank the Plasma System and Material (PSM) Company for assistance during this work.